WASHINGTON — The U.S. economy grew at a slightly faster 2 percent annual rate from July through September, buoyed by more spending by consumers and the federal government. Growth accelerated from the 1.3 percent rate in the April-June quarter, the Commerce Department said this morning. The report is the last snapshot of economic growth before Americans choose a president in 11 days. The pickup in growth could lend weight to President Barack Obama’s message that the economy is improving. Still, growth remains too weak to rapidly boost hiring. And the 1.74 percent annual growth rate for the first nine months of 2012 trails last year’s 1.8 percent growth, a point that Republican nominee Mitt Romney has emphasized. “Growth came in a little higher than we had feared, largely because of the big jump in federal spending,” said Paul Ashworth, chief U.S. economist at Capital Economics. “But the economy is still not growing rapidly enough to create sufficient jobs to reduce the unemployment rate.”